Robust Backup Solution

Context

Design and implementation of a complete backup solution for a city hall: Bash scripts with rsync supporting FULL, incremental and differential modes.

Objectives

• Develop parameterizable backup scripts
• Implement the three backup modes (FULL/INC/DIFF)
• Set up backup rotation and retention
• Create restoration scripts
• Automate via cron

Technologies Used

• Bash: scripting
• Rsync: file synchronization
• SSH: secure remote transfer
• Cron: task scheduling

Backup Types Comparison

FULL Backup (Complete)

Complete copy of all data at each execution.

Advantages	Disadvantages
Simple and fast restoration (single set)	Consumes a lot of disk space
Independent of previous backups	Long execution time
Maximum reliability	High bandwidth if remote

Incremental Backup (INC)

Copies only files modified since the last backup (FULL or INC).

Advantages	Disadvantages
Very fast to execute	Complex restoration (FULL + all INCs)
Minimal disk space	Dependency on complete chain
Low bandwidth	If one INC is corrupted, following ones are unusable

Differential Backup (DIFF)

Copies only files modified since the last FULL.

Advantages	Disadvantages
Simple restoration (FULL + last DIFF)	Size grows over time
Faster than FULL	Slower than INC
Fewer dependencies than INC	Requires more space than INC

Comparison Table

Criteria	FULL	INC	DIFF
Backup time	Long	Short	Medium
Space used	Large	Minimal	Growing
Restoration time	Short	Long	Medium
Restoration complexity	Low	High	Medium
Fault tolerance	Excellent	Low	Good

Script Architecture

backup/
├── backup.sh           # Main script
├── restore.sh          # Restoration script
├── config/
│   └── backup.conf     # Configuration
├── logs/
│   └── backup_YYYYMMDD.log
└── data/
    ├── FULL_20250801/
    ├── INC_20250802/
    └── latest -> INC_20250802/

Deliverables

Presentation

Presentation Slides (PDF)

Backup Scripts

sauvegarde_inc.sh - Incremental Backup

#!/bin/bash
# Author: BENE Mael
# Version: 1.2
# Description: Incremental backup with rotation, latest link, and automatic FULL management via folder name

set -euo pipefail

# Check parameters
if [ "$#" -lt 2 ]; then
    echo "Usage: $0 \"FOLDER1 FOLDER2 ...\" RETENTION_DAYS"
    exit 1
fi

# Parameters
DOSSIERS="$1"
RETENTION_JOURS="$2"

# Configuration
SOURCE_DIR="$HOME/mairie"
DEST_USER="backup-user"
DEST_HOST="stockage"
DEST_BASE="/home/$DEST_USER/backup"
LOG_DIR="$HOME/backup-logs"
DATE="$(date '+%Y-%m-%d_%H-%M-%S')"
CUMULATIVE_LOG="$LOG_DIR/sauvegardes_inc.log"

mkdir -p "$LOG_DIR"

# Log header
{
    echo "====================================================="
    echo "[$(date '+%F %T')] > START INCREMENTAL BACKUP"
    echo "Backed up folders: $DOSSIERS"
    echo "Planned retention: $RETENTION_JOURS day(s)"
    echo "Start timestamp: $DATE"
    echo "====================================================="
} >> "$CUMULATIVE_LOG"

# SSH connection check
if ! ssh -q "$DEST_USER@$DEST_HOST" exit; then
    echo "Error: unable to connect to $DEST_USER@$DEST_HOST"
    exit 2
fi

for dossier in $DOSSIERS; do
    echo "-----------------------------------------------------" >> "$CUMULATIVE_LOG"
    echo "[$(date '+%F %T')] > Processing folder: $dossier" >> "$CUMULATIVE_LOG"

    # Detect last FULL within retention period
    LAST_FULL=$(ssh "$DEST_USER@$DEST_HOST" "find '$DEST_BASE/$dossier' -maxdepth 1 -type d -name '*_FULL' -mtime -$RETENTION_JOURS 2>/dev/null" | sort -r | head -n 1)

    FORCE_FULL=0
    TYPE_SUFFIX=""

    if [ -z "$LAST_FULL" ]; then
        FORCE_FULL=1
        TYPE_SUFFIX="_FULL"
        echo "[$(date '+%F %T')] > No recent FULL found -> BACKUP TYPE: FULL" >> "$CUMULATIVE_LOG"
    else
        TYPE_SUFFIX="_INC"
        echo "[$(date '+%F %T')] > Backup TYPE: INCREMENTAL (base: $LAST_FULL)" >> "$CUMULATIVE_LOG"
    fi

    BACKUP_ID="${DATE}${TYPE_SUFFIX}"
    DEST_PATH="$DEST_BASE/$dossier/$BACKUP_ID"

    # Create destination folder
    ssh "$DEST_USER@$DEST_HOST" "mkdir -p '$DEST_PATH'" >> "$CUMULATIVE_LOG" 2>&1

    # rsync with or without link-dest
    if [ "$FORCE_FULL" -eq 1 ]; then
        rsync -av --delete -e ssh "$SOURCE_DIR/$dossier/" "$DEST_USER@$DEST_HOST:$DEST_PATH/" \
            >> "$CUMULATIVE_LOG" 2>&1
    else
        rsync -av --delete --link-dest="$LAST_FULL" -e ssh "$SOURCE_DIR/$dossier/" "$DEST_USER@$DEST_HOST:$DEST_PATH/" \
            >> "$CUMULATIVE_LOG" 2>&1
    fi

    echo "[$(date '+%F %T')] > End of backup for $dossier" >> "$CUMULATIVE_LOG"

    # Update latest symbolic link
    ssh "$DEST_USER@$DEST_HOST" bash -c "'
        cd \"$DEST_BASE/$dossier\"
        ln -sfn \"$BACKUP_ID\" latest
    '" >> "$CUMULATIVE_LOG" 2>&1

    # Rotation: keep $RETENTION_JOURS most recent (all types)
    ssh "$DEST_USER@$DEST_HOST" bash -c "'
        cd \"$DEST_BASE/$dossier\"
        ls -1dt 20* | tail -n +$((RETENTION_JOURS + 1)) | xargs -r rm -rf
    '" >> "$CUMULATIVE_LOG" 2>&1
done

echo "[$(date '+%F %T')] DAILY BACKUP COMPLETED" >> "$CUMULATIVE_LOG"
echo >> "$CUMULATIVE_LOG"

sauvegarde_dif.sh - Differential Backup

#!/bin/bash
# Author: BENE Mael
# Version: 1.1
# Description: Differential backup with execution time in logs

set -euo pipefail

# Configuration
DOSSIER="MACHINES"
SOURCE_DIR="$HOME/mairie/$DOSSIER"
DEST_USER="backup-user"
DEST_HOST="stockage"
DEST_PATH="/home/$DEST_USER/backup/$DOSSIER"
LOG_DIR="$HOME/backup-logs"
DATE="$(date '+%Y-%m-%d_%H-%M-%S')"
CUMULATIVE_LOG="$LOG_DIR/sauvegardes_dif.log"

mkdir -p "$LOG_DIR"

start=0
rsync_started=false

# Function executed even on crash or interruption
on_exit() {
    if $rsync_started; then
        local end=$(date +%s)
        local duration=$((end - start))
        echo "[$(date '+%F %T')] > Backup duration: ${duration} seconds" >> "$CUMULATIVE_LOG"
    fi
}
trap on_exit EXIT

# Start log
{
    echo "====================================================="
    echo "[$(date '+%F %T')] > START DIFFERENTIAL BACKUP"
    echo "Folder       : $DOSSIER"
    echo "Source       : $SOURCE_DIR"
    echo "Destination  : $DEST_USER@$DEST_HOST:$DEST_PATH"
    echo "Timestamp    : $DATE"
    echo "====================================================="
} >> "$CUMULATIVE_LOG"

# Prepare remote folder
echo "[$(date '+%F %T')] > Checking remote folder..." >> "$CUMULATIVE_LOG"
ssh "$DEST_USER@$DEST_HOST" "mkdir -p '$DEST_PATH'" >> "$CUMULATIVE_LOG" 2>&1
echo "[$(date '+%F %T')] > Remote folder ready." >> "$CUMULATIVE_LOG"

# Time measurement
start=$(date +%s)
rsync_started=true

# Launch rsync
echo "[$(date '+%F %T')] > Launching rsync..." >> "$CUMULATIVE_LOG"
rsync -av --inplace --partial --append -e ssh "$SOURCE_DIR/" "$DEST_USER@$DEST_HOST:$DEST_PATH/" \
    >> "$CUMULATIVE_LOG" 2>&1

# If rsync finished normally, continue logging
echo "[$(date '+%F %T')] DIFFERENTIAL BACKUP COMPLETED" >> "$CUMULATIVE_LOG"
echo >> "$CUMULATIVE_LOG"

Restoration Scripts

restore_inc.sh - Incremental Restoration

#!/bin/bash
# Author: BENE Mael
# Version: 1.1
# Description: Interactive restoration of a folder or individual file (improved version with logging)

set -euo pipefail

# Configuration
DEST_USER="backup-user"
DEST_HOST="stockage"
DEST_BASE="/home/$DEST_USER/backup"
BASE_RESTORE_DIR="/home/oclassroom/mairie"
LOG_FILE="/home/oclassroom/backup-logs/restores_inc.log"

# Log function
log_header() {
    local type="$1"  # "Complete folder" or "Specific file"
    {
        echo "====================================================="
        echo "[$START_DATE] > START INCREMENTAL RESTORATION"
        echo "Restored folder: $DOSSIER"
        echo "Type: $type"
        echo "Backup timestamp: $BACKUP_TIMESTAMP"
        echo "====================================================="
    } >> "$LOG_FILE"
}

# List available folders (excluding MACHINES)
DIR_LIST=$(ssh "$DEST_USER@$DEST_HOST" "ls -1 $DEST_BASE" | grep -v '^MACHINES$')
if [ -z "$DIR_LIST" ]; then
    echo "No backup folder found."
    exit 1
fi

echo "Folders available for restoration:"
DIR_ARRAY=()
i=1
while read -r line; do
    echo " $i) $line"
    DIR_ARRAY+=("$line")
    ((i++))
done <<< "$DIR_LIST"

read -rp "Folder number to restore: " DIR_NUM
DOSSIER="${DIR_ARRAY[$((DIR_NUM - 1))]}"

# List available backups
BACKUP_LIST=$(ssh "$DEST_USER@$DEST_HOST" "ls -1dt $DEST_BASE/$DOSSIER/20*_* 2>/dev/null")

if [ -z "$BACKUP_LIST" ]; then
    echo "No backup found for $DOSSIER."
    exit 1
fi

echo "Available backups for '$DOSSIER':"
BACKUP_ARRAY=()
i=1
while read -r line; do
    SHORT=$(echo "$line" | sed "s|$DEST_BASE/||")
    echo " $i) $SHORT"
    BACKUP_ARRAY+=("$line")
    ((i++))
done <<< "$BACKUP_LIST"

read -rp "Backup number to restore (Enter = latest): " BACKUP_NUM
if [ -z "$BACKUP_NUM" ]; then
    SELECTED_BACKUP=$(ssh "$DEST_USER@$DEST_HOST" "readlink -f '$DEST_BASE/$DOSSIER/latest'" || true)
    if [ -z "$SELECTED_BACKUP" ]; then
        echo "No 'latest' link found for this folder."
        exit 1
    fi
else
    SELECTED_BACKUP="${BACKUP_ARRAY[$((BACKUP_NUM - 1))]}"
fi

echo "Selected backup: $(echo "$SELECTED_BACKUP" | sed "s|$DEST_BASE/||")"

# Timestamp for logs
START_DATE=$(date '+%Y-%m-%d %H:%M:%S')
BACKUP_TIMESTAMP=$(basename "$SELECTED_BACKUP")

# Choose between complete restoration or specific file
echo "What do you want to restore?"
select CHOIX in "Complete folder" "Specific file"; do
    case $REPLY in
        1)
            RESTORE_PATH="$BASE_RESTORE_DIR/$DOSSIER"
            echo "> Complete restoration to: $RESTORE_PATH"
            mkdir -p "$RESTORE_PATH"
            log_header "Complete folder"
            rsync -av -e ssh "$DEST_USER@$DEST_HOST:$SELECTED_BACKUP/" "$RESTORE_PATH/" >> "$LOG_FILE" 2>&1
            echo "Folder restored successfully."
            break
            ;;
        2)
            echo "List of available files:"
            FILE_LIST=$(ssh "$DEST_USER@$DEST_HOST" "cd '$SELECTED_BACKUP' && find . -type f" | sed 's|^\./||')
            if [ -z "$FILE_LIST" ]; then
                echo "No file found in backup."
                exit 1
            fi

            FILE_ARRAY=()
            i=1
            while read -r file; do
                echo " $i) $file"
                FILE_ARRAY+=("$file")
                ((i++))
            done <<< "$FILE_LIST"

            read -rp "File number to restore: " FILE_NUM
            FILE_TO_RESTORE="${FILE_ARRAY[$((FILE_NUM - 1))]}"
            DEST_PATH="$BASE_RESTORE_DIR/$DOSSIER/$(dirname "$FILE_TO_RESTORE")"
            mkdir -p "$DEST_PATH"
            log_header "Specific file"
            echo "> Restoring '$FILE_TO_RESTORE' to '$DEST_PATH'" >> "$LOG_FILE"
            rsync -av -e ssh "$DEST_USER@$DEST_HOST:$SELECTED_BACKUP/$FILE_TO_RESTORE" "$DEST_PATH/" >> "$LOG_FILE" 2>&1
            echo "File restored successfully."
            break
            ;;
        *)
            echo "Invalid choice."
            ;;
    esac
done

restore_dif.sh - Differential Restoration

#!/bin/bash
# Author: BENE Mael
# Version: 1.1
# Description: Manual differential backup restoration (VMs) with cumulative logging

set -euo pipefail

# Configuration
DOSSIER="MACHINES"
DEST_USER="backup-user"
DEST_HOST="stockage"
DEST_PATH="/home/$DEST_USER/backup/$DOSSIER"
RESTORE_DIR="$HOME/mairie/$DOSSIER"
LOG_FILE="$HOME/backup-logs/restores_dif.log"

mkdir -p "$HOME/backup-logs"
mkdir -p "$RESTORE_DIR"

START_DATE=$(date '+%Y-%m-%d %H:%M:%S')

{
    echo "====================================================="
    echo "[$START_DATE] > START DIFFERENTIAL RESTORATION"
    echo "Restored folder: $DOSSIER"
    echo "Local destination: $RESTORE_DIR"
    echo "Remote source: $DEST_USER@$DEST_HOST:$DEST_PATH"
    echo "====================================================="
} >> "$LOG_FILE"

# Restoration with rsync (differential)
rsync -av -e ssh "$DEST_USER@$DEST_HOST:$DEST_PATH/" "$RESTORE_DIR/" >> "$LOG_FILE" 2>&1

{
    echo "[$(date '+%Y-%m-%d %H:%M:%S')] > END OF RESTORATION"
    echo
} >> "$LOG_FILE"

Cron Configuration

crontab - Backup Scheduling

# Differential backup of VM that forces stop after 3h (so at 4am)
0 1 * * * timeout 3h /home/oclassroom/backup_script/backup/differentielle.sh

# Daily backups with 7 days retention
0 4 * * * /home/oclassroom/backup_script/backup/incrementale.sh "FICHIERS" 7
0 5 * * * /home/oclassroom/backup_script/backup/incrementale.sh "MAILS" 7
0 6 * * * /home/oclassroom/backup_script/backup/incrementale.sh "RH" 7
30 6 * * * /home/oclassroom/backup_script/backup/incrementale.sh "TICKETS" 7

# SITE backup every 3 days at 7am, with 15 days retention
0 7 */3 * * /home/oclassroom/backup_script/backup/incrementale.sh "SITE" 15

Execution Logs

sauvegardes_inc.log - Incremental Backup Logs

=====================================================
[2025-08-12 12:00:00] > START INCREMENTAL BACKUP
Backed up folders: FICHIERS
Planned retention: 7 day(s)
Start timestamp: 2025-08-12_12-00-00
=====================================================
-----------------------------------------------------
[2025-08-12 12:00:00] > Processing folder: FICHIERS
[2025-08-12 12:00:00] > No recent FULL found -> BACKUP TYPE: FULL
sending incremental file list
./
doc1.txt
doc2.txt
fichier_2025-08-12_1.txt
fichier_2025-08-12_2.txt

sent 449 bytes  received 95 bytes  1.088,00 bytes/sec
total size is 94  speedup is 0,17
[2025-08-12 12:00:01] > End of backup for FICHIERS
[2025-08-12 12:00:01] DAILY BACKUP COMPLETED

=====================================================
[2025-08-13 12:00:00] > START INCREMENTAL BACKUP
Backed up folders: FICHIERS
Planned retention: 7 day(s)
Start timestamp: 2025-08-13_12-00-00
=====================================================
-----------------------------------------------------
[2025-08-13 12:00:00] > Processing folder: FICHIERS
[2025-08-13 12:00:00] > Backup TYPE: INCREMENTAL (base: /home/backup-user/backup/FICHIERS/2025-08-12_12-00-00_FULL)
sending incremental file list
./
fichier_2025-08-13_1.txt
fichier_2025-08-13_2.txt

sent 361 bytes  received 57 bytes  836,00 bytes/sec
total size is 154  speedup is 0,37
[2025-08-13 12:00:01] > End of backup for FICHIERS
[2025-08-13 12:00:01] DAILY BACKUP COMPLETED

=====================================================
[2025-08-20 12:00:00] > START INCREMENTAL BACKUP
Backed up folders: FICHIERS
Planned retention: 7 day(s)
Start timestamp: 2025-08-20_12-00-00
=====================================================
-----------------------------------------------------
[2025-08-20 12:00:00] > Processing folder: FICHIERS
[2025-08-20 12:00:00] > No recent FULL found -> BACKUP TYPE: FULL
sending incremental file list
[...]
[2025-08-20 12:00:01] > End of backup for FICHIERS
[2025-08-20 12:00:01] DAILY BACKUP COMPLETED

sauvegardes_dif.log - Differential Backup Logs

=====================================================
[2025-08-12 17:26:10] > START DIFFERENTIAL BACKUP
Folder       : MACHINES
Source       : /home/oclassroom/mairie/MACHINES
Destination  : backup-user@stockage:/home/backup-user/backup/MACHINES
Timestamp    : 2025-08-12_17-26-10
=====================================================
[2025-08-12 17:26:10] > Checking remote folder...
[2025-08-12 17:26:10] > Remote folder ready.
[2025-08-12 17:26:10] > Launching rsync...
sending incremental file list
./
fichier_gros.test
rsync error: unexplained error (code 255) at rsync.c(716) [sender=3.2.7]
[2025-08-12 17:26:35] > Backup duration: 25 seconds

=====================================================
[2025-08-12 17:26:42] > START DIFFERENTIAL BACKUP
Folder       : MACHINES
Source       : /home/oclassroom/mairie/MACHINES
Destination  : backup-user@stockage:/home/backup-user/backup/MACHINES
Timestamp    : 2025-08-12_17-26-42
=====================================================
[2025-08-12 17:26:42] > Checking remote folder...
[2025-08-12 17:26:42] > Remote folder ready.
[2025-08-12 17:26:42] > Launching rsync...
sending incremental file list
./
fichier_gros.test

sent 668.597.769 bytes  received 38 bytes  148.577.290,44 bytes/sec
total size is 5.368.709.120  speedup is 8,03
[2025-08-12 17:26:46] DIFFERENTIAL BACKUP COMPLETED

[2025-08-12 17:26:46] > Backup duration: 4 seconds

restores_inc.log - Incremental Restoration Logs

=====================================================
[2025-08-12 17:23:56] > START INCREMENTAL RESTORATION
Restored folder: FICHIERS
Type: Specific file
Backup timestamp: 2025-08-25_12-00-00_INC
=====================================================
> Restoring 'doc1.txt' to '/home/oclassroom/mairie/FICHIERS/.'
receiving incremental file list
doc1.txt

sent 43 bytes  received 139 bytes  121,33 bytes/sec
total size is 18  speedup is 0,10

=====================================================
[2025-08-12 17:24:13] > START INCREMENTAL RESTORATION
Restored folder: FICHIERS
Type: Complete folder
Backup timestamp: 2025-08-25_12-00-00_INC
=====================================================
receiving incremental file list
./
doc2.txt
fichier_2025-08-12_1.txt
[...]
fichier_2025-08-25_2.txt

sent 578 bytes  received 2.750 bytes  6.656,00 bytes/sec
total size is 862  speedup is 0,26

restores_dif.log - Differential Restoration Logs

=====================================================
[2025-08-12 17:29:42] > START DIFFERENTIAL RESTORATION
Restored folder: MACHINES
Local destination: /home/oclassroom/mairie/MACHINES
Remote source: backup-user@stockage:/home/backup-user/backup/MACHINES
=====================================================
receiving incremental file list
./
fichier_1Go.bin
fichier_gros.test

sent 65 bytes  received 6.444.024.019 bytes  186.783.306,78 bytes/sec
total size is 6.442.450.944  speedup is 1,00
[2025-08-12 17:30:16] > END OF RESTORATION

Skills Acquired

• Advanced Bash script development
• Mastery of rsync and its options
• Backup strategy design (3-2-1)
• Retention and rotation management
• Automation with cron
• Restoration procedure documentation